Radiosurgery for unruptured cerebral arteriovenous
malformations

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ARTICLESRadiosurgery for unrupturedcerebral arteriovenous malformationsLong-term seizure outcomeSeung-Yeob Yang, MD,ABSTRACTMScObjective: To date, seizures in relation to arteriovenous malformations (AVM) have been a secondaryDong Gyu Kim, MD,target of most studies. The insufficient evaluation, in conjunction with the lack of consistent seizurePhDoutcome assessment, has made it been difficult to draw conclusions about seizure outcome afterHyun-Tai Chung, PhDradiosurgery for AVM. This study aimed to determine the effect of radiosurgery on seizure outcomeSun Ha Paek, MD, PhDdepending on AVM obliteration and on the development of new seizure in patients with AVM.Methods: Between 1997 and 2006, 161 consecutive patients underwent radiosurgery for un-Correspondence & reprintruptured AVM and were retrospectively assessed with a mean follow-up of 89.8 months by theirrequests to Dr. Kim:medical records, updated clinical information, and, when necessary, direct patient contact. Sei-[email protected]zure outcome was assessed using the Engel seizure frequency scoring system.Results: Of the 86 patients with a history of seizure before radiosurgery, 76.7% (66/86) wereseizure-free and 58.1% (50/86) were medication-free at the last follow-up visit. Of the patientswho achieved AVM obliteration, 96.7% (58/60) were seizure-free while 30.8% (8/26) of thosepatients who did not achieve AVM obliteration were seizure-free (p0.001). The proportion ofpatients who were medication-free was 81.7% (49/60) of the patients with obliteration and3.8% (1/26) of patients without obliteration (p0.001). Of the 75 patients with no history ofseizure before radiosurgery, 10 had provoked seizures due to the direct and indirect radiosurgicalinfluences after radiosurgery.Conclusions: Although radiosurgery tends to cause seizures temporarily, the radiosurgery mayimprove seizure outcomes in patients with AVM-related seizures, especially in patients with AVMobliteration. Neurology(R) 2012;78:1292-1298GLOSSARYAEDantiepileptic drug; ARUBAA Randomized Multicenter Clinical Trial of Unruptured Brain AVMs; AVMarterio-venous malformation; CIconfidence interval; GKgamma knife; ORodds ratio; PRIpostradiosurgery imaging.Until now, the prognosis of epilepsy-associated cerebral arteriovenous malformations (AVMs)has received little attention. Similar to the decreased risk of hemorrhage from cerebral AVMsfollowing stereotactic radiosurgery,1 seizure improvement may also be common in patientswith cerebral AVMs who undergo radiosurgery.2,3 Unfortunately, most of the available data inthis field come from studies that have assessed the patients at less than 5 years followingradiosurgery, and no study has investigated the long-term seizure outcome beyond 5 years.Moreover, it has been unclear whether, and to what extent, seizure frequency decreases bothduring a latency period and after AVM obliteration, compared to seizure frequency beforeradiosurgery. The impact of angiographic obliteration on seizure freedom and cessation ofEditorial, page 1286antiepileptic drugs (AEDs) after radiosurgery also remains unknown. In order to address thelong-term seizure outcome of AVM radiosurgery and the development of new seizures afterSupplemental data atwww.neurology.orgradiosurgery, we performed a retrospective study on 161 patients who had undergone radiosur-gery for their unruptured AVM.Supplemental DataFrom the Department of Neurosurgery (S.-Y.Y.), Dongguk University Graduate School, Seoul; and Department of Neurosurgery (D.G.K., H.-T.C.,S.H.P.), Seoul National University College of Medicine, Seoul, Korea.Go to Neurology.org for full disclosures. Disclosures deemed relevant by the authors, if any, are provided at the end of this article.1292Copyright (c) 2012 by AAN Enterprises, Inc.Table 1Distribution of patients by seizure frequency scoring systemBeforeFor the firstAt the lastradiosurgeryyearfollow-upSeizure frequencyScoreNo.%No.%No.%Seizure-free, off antiepileptic drug01922.15058.1Seizure-free, need for antiepileptic drug144.667.0unknownSeizure-free, requires antiepileptic drugs to211.21112.8remain soNondisabling simple partial seizures31517.42023.389.3Nondisabling nocturnal seizures only411.21-3 per year54855.82225.689.34-11 per year61011.61112.81-3 per month71011.644.611.21-6 per week822.333.511.21-3 per day911.222.34-10 per day10>10 per day but not status epilepticus11Status epilepticus without barbiturate coma12METHODS Patients. Between 1997 and 2006, 411 consec-partial, and partial with secondary generalization or generalizedutive patients with an angiographically proven cerebral AVMseizures. Preradiosurgical seizure frequency score was defined asunderwent gamma knife (GK) radiosurgery at our hospital. Ofthe score for the year preceding radiosurgery. In order to assessthe 411 patients, 14 were lost during follow-up, and were ex-the early effect of radiosurgery on seizure outcomes before AVMcluded from this study because the follow-up after radiosurgeryobliteration, we investigated seizure frequency score for the firstwas less than 1 year or data were insufficient to record an Engelyear after radiosurgery. For this evaluation, the "at the lastseizure frequency score (table e-1 on the Neurology(R) Web site atfollow-up" postradiosurgical outcome was assessed during thewww.neurology.org). It is difficult to precisely evaluate the effectlast 12 months preceding the analysis of data. Seizure freedomof radiosurgery on seizure outcome in patients who had experi-and cessation of medication were defined as seizure frequencyenced hemorrhages because of the epileptogenic effect of hemor-scores of 0 -2 and score 0, respectively.9 To assess the effect of therhage.4-6 Therefore, we excluded the 236 patients who hadpreradiosurgical seizure frequency or duration on seizure out-experienced intracranial hemorrhages before radiosurgery. In all,come, the patients who had presented with seizure were divided161 patients were enrolled in this study to assess the long-term sei-into 2 groups: patients with only a single seizure and patientszure outcome and the epileptogenic effect of radiosurgery (tablewith more than 1 seizure before radiosurgery.e-1). None of these 161 patients had any other brain lesions causingseizures, progressive CNS disorders, or psychotic problems.Statistical analysis. The median time to achieve seizure free-dom or cessation of medication was determined on the basis ofStandard protocol approvals, registrations, and patientKaplan-Meier event-free survival curves. Associations betweenconsents. The Institutional Review Board of our hospital ap-categorical variables and seizure outcome were analyzed usingproved all aspects of the study. However, it did not require in-Pearson 2 test (or Fisher exact test as appropriate). Continuousformed consent from these patients for their inclusion becausevariables were compared using Student t tests. Prognostic factorsthe study depended only on information obtained as a part ofconsidered for univariate analysis included patient demograph-routine clinical care and patient medical records.ics, Spetzler-Martin grade, seizure frequency score before radio-Radiosurgical technique and follow-up evaluations.surgery, single seizure only before radiosurgery, embolizationThe radiosurgical technique used was reported previously.7 De-before radiosurgery, duration of epilepsy before radiosurgery,tailed description of the follow-up evaluations is provided as ap-type and onset of seizures, switch or increment of AEDs afterpendix e-1. AVM characteristics and radiosurgical parametersradiosurgery, and AVM obliteration after radiosurgery. Multi-are summarized in table e-1.variable logistic regression analysis was used to assess the associa-The postradiosurgery imaging (PRI) changes were defined astion of variables with seizure freedom or off medication. Tothe development of signal changes on follow-up T2-weighted orcontrol multicollinearity, radiation dose, AVM volume, andfluid-attenuated inversion recovery MRI, regardless of whetherAVM size from the regression analysis (all variance inflation fac-these changes were accompanied by symptoms. The severity oftor values10.0) were omitted. Results are presented as ad-PRI changes was classified as mild, moderate, or severe accordingjusted odds ratios (OR) with a 95% confidence interval (CI).to our previous report.8The level of statistical significance was set as p0.05.Assessment of seizure outcomes. We assessed seizure out-come by comparing the preradiosurgical and postradiosurgicalRESULTS Seizure development after radiosurgery.seizure frequencies using the Engel seizure frequency scoring sys-Of the 75 patients with no history of seizures beforetem (table 1).9 Seizures were classified as simple partial, complexradiosurgery, no patient was on AEDs before and atNeurology 78 April 24, 20121293FigureSeizure outcome after radiosurgery (n86)(A) The probability of seizure freedom (54.7% at 2 years and 73.3% at 5 years). (B) The probability of off medication(30.2% at 2 years and 54.7% at 5 years).the time of radiosurgery. The mean clinical and neu-The distribution of patients by seizure frequencyroradiologic follow-up periods after radiosurgeryscore before radiosurgery, for the first year, and at thewere 89.2 and 56.2 months, respectively. At the lastlast follow-up are presented in table 1. For the firstfollow-up, angiographically proven AVM oblitera-year after radiosurgery, 27.9% (24/86) of patientstion was observed in 61 of the 75 patients. Of the 75were seizure-free while 3.5% (3/86) of patients hadpatients, 10 had provoked seizures after radiosurgery.an increased seizure frequency score. However, thereOf these 10 patients, 1 developed a partial seizurewas a difference in the proportion with seizure free-within 24 hours after radiosurgery without neuroim-dom ( p0.001). Of the 3 patients with increasedaging changes, but no recurrence was seen withoutseizure frequency score for the first year, only 1 re-medication ever since; 5 had provoked seizures sev-ported a worsening of seizure at the last follow-up.eral months to years after radiosurgery due to severeThe seizure frequency scores were different betweenPRI changes, but no recurrence was seen after thebefore radiosurgery and at last follow-up ( presolution of the PRI changes; and 4 had provoked0.001). At the last follow-up, 76.7% (66/86) of pa-seizures due to latency period hemorrhages.tients were seizure-free; 96.7% (58/60) of patientsSeizure freedom. Of the 86 patients with a history ofwho achieved AVM obliteration were seizure-free;seizures before radiosurgery, 72 (84%) were followedand 30.8% (8/26) of those who did not achievefor at least 5 years. The mean clinical and neurora-AVM obliteration were seizure-free ( p0.001). Pa-diologic follow-up periods after radiosurgery weretients with AVM obliteration remained seizure-free90.2 and 57.5 months, respectively. At the lastat the last follow-up, but 2 of the 26 patients who didfollow-up, angiographically proven AVM oblitera-not experience AVM obliteration had a relapse oftion was observed in 60 of the 86 patients.seizures during AED tapering. The median time toProvoked seizures occurred in 3 patients withinachieve seizure freedom after radiosurgery was 2.024 hours after radiosurgery without apparent neuro-years (95% CI 1.5-2.5) (figure, A).imaging changes, but all of these patients remainedThe results after univariate analysis based on dif-seizure-free subsequently. Four patients had in-ferent parameters are given in table 2. Multivariatecreased seizure frequency several months to years af-analysis defined 2 independent prognostic factorster radiosurgery probably due to severe PRI changes,predicting seizure freedom: AVM obliteration ( pbut no recurrence was seen after the resolution of the0.001) and seizure frequency score before radiosur-PRI changes. At the last follow-up, the 4 patientsgery ( p0.011) (table 2).were medication-free, and they all achieved AVMPrior to radiosurgery, 36% (31/86) of patientsobliteration. The PRI changes were not associatedhad a single seizure only; the remainder of the pa-with either seizure freedom ( p0.376) or going offtients had more than one seizure. At the last follow-medication ( p0.309) at the last follow-up.up, 90.3% (28/31) of the patients with only a single1294Neurology 78 April 24, 2012seizure were seizure-free; 100% (25/25) of patientswho achieved AVM obliteration were seizure-free;0.001p0.0450.4360.212and 50% (3/6) of those who did not achieve AVMobliteration were seizure-free ( p0.004) (table 3).Patients with only a single seizure tended to achieve ahigher seizure-free rate than patients with more thanCIone seizure (90.3% vs 69.1%); however, this differ-1.02-3.760.38-9.520.77-3.29ence was not significant in the multivariate analysis95%16.08-1752.41( p0.055). Although the correlation betweenseizure-free and seizure duration before radiosurgery1.961.901.59was not significant, there was a tendency for a shorterMultivariateOR167.85mean duration in seizure-free patients than in thosewho were not seizure-free at the last follow-up (35.3months vs 49.6 months, respectively).0.001p0.0360.0230.1150.1820.0060.5680.6950.3060.309Off medication. Of the 86 patients with a history ofseizures before radiosurgery, all patients were onAEDs before radiosurgery: 62 were taking one kindCIof AED, 21 were taking 2 kinds of AEDs, and 3 were1.03-2.131.14-7.810.99-1.060.99-1.011.21-3.170.74-1.710.41-3.820.99-1.020.93-1.02medication95%13.59-912.17taking 3 kinds of AEDs. At the last follow-up, 50fopatients were off AEDs, 23 were taking one kind ofAED, 11 were taking 2 kinds of AEDs, and 2 were1.482.981.031.011.961.131.251.010.98taking 3 kinds of AEDs. However, either AEDs wereCessationUnivariateOR111.36radiosurgery.switched or their doses were increased in 6 patients:AEDs were switched once in 4 patients, twice in oneRSp0.0010.0110.0550.751patient, and doses were increased in another patient.AED modification was not associated with seizureimaging;freedom ( p0.353). At the last follow-up, 50 of thepatients were medication-free, whose follow-up pe-riod after cessation of medication was from 4 to 133CImonths (mean 67 months). The proportions of1.33-9.040.93-577.250.37-4.0395%13.31-16829.68medication-free patients with and without an AVMpostradiosurgeryobliteration were 81.7% (49/60) and 3.8% (1/26),PRIrespectively ( p0.001). The median time to3.461.2123.25MultivariateOR473.34achieve the cessation of medication after radiosurgeryratio;was 4.0 years (95% CI 2.8 -5.2) (figure, B).oddsThe results after univariate analysis based onradiosurgery0.001p0.0010.0330.1160.4200.0120.9000.7530.3530.376different parameters are given in table 3. Multivar-ORafteriate analysis revealed that AVM obliteration ( p0.001) and seizure frequency score before radio-interval;surgery ( p0.045) were associated with going offoutcomeCImedication (table 2).1.36-3.631.11-15.640.99-1.070.97-1.011.16-3.410.63-1.670.35-5.460.45-9.630.92-1.0395%12.69-335.45At the last follow-up, 74.2% (23/31) of the pa-seizureconfidencefreedomtients with only a single seizure were off AEDs; 92%withCI(23/25) of patients who achieved AVM obliteration2.224.171.031.001.991.031.392.070.97SeizureUnivariateOR65.25drug;were off AEDs; and 0% (0/6) of those who did notachieve AVM obliteration were off AEDs ( passociatedSR0.001) (table 3).SAEDsRSantiepilepticComplications.DetaileddescriptionofthebeforeRofscoretyperadiosurgery-related complications is provided asgradeParametersbeforebeforeAEDappendix e-2.seizureepilepsyfoseizureincrementfrequencySr2RseizurefirstoobliterationDISCUSSION We found that radiosurgery is effec-atchangestive for seizure control even before AVM oblitera-TableParameterAVMSeizurebeforeSingleAgeDurationSpetzler-MartinPrincipalEmbolizationSwitchPRIAbbreviations:tion, although the radiosurgery tends to causeNeurology 78 April 24, 20121295Table 3Relation between single seizure only before RS and seizure outcomeaPatients with only a single seizure beforePatients with more than one seizure beforeRS (n31)RS (N 55)AVM obliterationAVM obliterationAVM obliterationAVM obliteration( ) (n25)( ) (n6)p( ) (n35)( ) (n20)pSeizure freedom,/25 (100)/0 (0)3 (50.0)/3 (50.0)0.00433 (94.3)/2 (5.7)5 (25.0)/15 (75.0)0.001Cessation of23 (92.0)/2 (8.0)0 (0)/6 (100)0.00126 (74.3)/9 (25.7)1 (5.0)/19 (95.0)0.001medication,/Abbreviations: AVMarteriovenous malformation; RSradiosurgery.a Data are number (%) of patients.seizures temporarily. A number of studies have dem-correlation between seizure outcome and AVMonstrated that the seizure frequency begins to de-obliteration, but that there is a tendency for a bettercrease several months after radiosurgery and that theseizure outcome for patients with obliterated AVMs.reduction of seizure frequency and intensity does notA possible explanation may simply be that while theyseem to require AVM obliteration or morphologicanalyzed patients at the fixed time points of 1 and 3changes.2,6,10-13 The results from our study are con-years following radiosurgery, our study was focusedsistent with these results. Although all patients didon the patients with more than 4 years of follow-upnot experience AVM obliteration 1 year after radio-after radiosurgery. They showed that AVM diametersurgery, 24 patients became seizure-free, and 19 ofis associated with an excellent seizure outcome not atthese 24 patients achieved cessation of medication.the first year of follow-up, but at year 3 of follow-up.At the last follow-up, 8 of 26 patients without AVMThey also noted that longer follow-up is necessary toobliteration became seizure-free, and 1 of these 8 pa-more accurate assessment of the role of radiosurgery.tients discontinued medication. These findings sug-Prior studies have shown that patients with longergest that radiosurgery can reduce seizure frequencyseizure history and frequent seizures had a poorer sei-and intensity via some intrinsic effects on the AVMzure outcome than those without longer seizure his-nidus and surrounding area.6,12,13 The suppression oftory and frequent seizures.2,3,19-21 Our study isepileptic activity by a neuromodulatory effect at non-consistent with these results, which seems to be asso-necrotizing radiation doses has been proposed as pos-ciated with the development of secondary epilepto-sible intrinsic effects.13-16 Biochemically, radiationgenic foci distant from the AVM that, consequently,has been hypothesized to inhibit protein synthesis,were not irradiated. Secondary epileptogenesis haspreventing the maintenance of spontaneous neuronbeen already described in patients with epilepsybursts,16 and have differential effects on the inhibi-caused by AVMs.19-21tory GABA system and the excitatory amino acid sys-Seizure improvement is quite common in patientstem.14,15 Accordingly, it might be possible to modifywith AVMs who have undergone radiosurgery andthe brain region adjacent to the AVM to make itrivals the results provided by microsurgical resectionnonepileptic while preserving its functional role.14,15of AVMs2,3,6,11,13,17,18,21,22; 70.4%- 83.0% of AVMIn our study, 27.9% of patients were seizure-free 1patients with preoperative seizure became seizure-year after radiosurgery, and 76.7% of patients werefree or had occasional auras after microsurgical re-seizure-free at the last follow-up. These findings sug-section.21,22 The seizure improvement achieved bygest ongoing changes after radiosurgery in the AVMradiosurgery warrants the use of this technique innidus and surrounding area. Recent studies have re-patients with medically refractory seizures, butported that more patients with AVM obliterationmicrosurgery is perhaps preferable to radiosurgerywere seizure-free than patients without.3,17 The re-in terms of the immediate prevention of further hem-sults from our study show a similar outcome. Basedorrhages.21,22 However, in addition to microsurgery-on our findings and those of others,3,17,18 althoughrelated complications, microsurgical resection mayradiosurgery has beneficial effects on seizure out-create a new seizure focus and may increase seizurecomes even before AVM obliteration, higher seizure-frequency due to cortical or subcortical damage byfree rates were observed in patients with AVMmanipulation; 16.3-31.6% of AVM patients with-obliteration. In addition to the neuromodulatory ef-out a history of preoperative seizures had new onsetfect of irradiation mentioned above, radiosurgical re-seizures.22,23 In our study, mean radiologic follow-upduction of the steal phenomenon may additionallywas 56.8 months during which 10 instances of AVMcontribute to the reduction of epileptogenic activityrupture occurred leading to a hemorrhage rate ofin the ischemic areas surrounding an AVM.3,10,11,17,18minimum 1.3% per year until obliteration; compara-However, a recent study2 showed that there is noble findings have also been reported.2,17 This suggests1296Neurology 78 April 24, 2012slightly higher bleeding risk in unruptured brainThe gold standard for evaluating the effect of radio-AVMs following radiosurgery as compared to naturalsurgery on seizure outcome would be a randomized trialhistory.24-26 These series on the natural history reflectcomparing a group undergoing radiosurgery with aa selection bias regarding AVM size, location, andgroup receiving medication only. However, there haveother clinical and anatomic characteristics and com-not been any randomized trials comparing any of theparisons between published data and our series haveforms of interventional therapy (with endovascular pro-to be made with caution.cedures, microsurgery, or radiosurgery, alone or inA recent study reported that 13 of the 65 patientscombination) for AVMs among themselves or withexamined had provoked seizures several months tomedical management. A new trial, A Randomizedyears after radiosurgery due to low AED levels or dueMulticenter Clinical Trial of Unruptured Brainto edema as confirmed by neuroimaging.2 In anotherAVMs (ARUBA),27 began in 2006 to determinestudy, 10 of the 80 patients with PRI changes hadwhether medical management improves long-termprovoked seizures; however, seizures were controlledoutcomes of patients with unruptured AVMs com-with or without AEDs, and no other interventionpared to interventional therapy, and is ongoing. Thewas needed.5 In our study, 9 of the 161 patients hadARUBA dataset includes data on seizure recur-problems with new or increased seizure activity thatrence on prospective follow-up in patients with orrelated to PRI changes, but the PRI changes were notwithout complete AVM obliteration. According toultimately associated with seizure outcomes at thethe supporting data of the ARUBA study, radio-last follow-up. Based on the findings of our studysurgery may increase the risk of hemorrhage andand those of others,2,5 although the PRI changes mayinduce a disabling persisting clinical syndrome inbe an important seizure-inducing factor, this effectAVM patients who have not yet bled. Neverthe-seems to be working temporarily until the resolutionless, while we await the results of the ongoingof the PRI changes.ARUBA study, we consider radiosurgery inOur study has some limitations that need to bepatients with a cerebral AVM because of theconsidered. Due to treatment selection (AVMs treat-beneficial effects of radiosurgery in terms of angio-able by radiosurgery) and referral pattern, clinical pa-graphic cure, prevention of hemorrhage, and im-tient characteristics may be subject to systematic biasprovement of seizure outcome.1-3,6,11,13,17 Weand influence the outcome of the analysis.performed a retrospective observational study andTo analyze the association between AVM radio-did not include a control group of patients; neverthe-surgery and seizures, a direct comparison of 2 groups'less, the relatively large size and long-termoutcomes (ruptured vs unruptured AVM before ra-follow-up of our cohort make it well-suited to andiosurgery) could provide more information. How-assessment of seizure outcomes of radiosurgery.ever, seizure focus can be generated there byAlso, the results of this study will be interesting tomechanical compression, ischemic insult, and stimu-compare to the results of the ARUBA study.lation by hematoma or hemosiderin deposits and byresultant gliosis in surrounding brain.4-6 Because ofAUTHOR CONTRIBUTIONSthe epileptogenic effect of hemorrhage as above, it isDr. Yang and Dr. Kim developed the hypothesis for this study and wrotehard to assess the clear association between the AVMthe first draft. Analysis of clinical data was done principally by Dr. Yang,Dr. Kim, and Dr. Chung. All authors contributed to data interpretation.radiosurgery and seizures. Therefore, the direct com-Dr. Yang, Dr. Kim, Dr. Paek, and Dr. Chung critically revised the firstparison between 2 groups will be left an area for fu-draft and approved the final manuscript.ture research.A potential problem is the delay in confirmingACKNOWLEDGMENTAVM obliteration. The exact date of AVM oblitera-The authors thank Dr. Sang Gun Lee (Seoul National University, Seoul)tion was unclear because obliteration was only iden-for providing insight in the planning stages of the study; Dr. Jung HoHan and Sang Sun Chung, RN (Seoul National University Hospital,tified at the time of angiography. Serial imaging wasSeoul), who collected data for this study; and Dr. Byung Joo Park (Seoulperformed every 6 months, and angiography was rec-National University, Seoul) and the Medical Research Collaboratingommended at 3 years after radiosurgery. For patientsCenter at Seoul National University Hospital for their assistance inwhose AVM had disappeared on CT or MRI afterstatistical analysis. Dr. Moon Hee Han (Seoul National University,Seoul) helped us review the neuroradiologic findings of cerebral arte-radiosurgery, angiography was performed earlier.riovenous malformations.Therefore, we assume that AVM obliteration oc-curred a maximum of 6 months earlier than its con-DISCLOSUREfirmation by angiography. For this reason, weThe authors report no disclosures relevant to the manuscript. Go toanalyzed the data, including the data during the firstNeurology.org for full disclosures.year after radiosurgery, to assess the effect of radio-surgery on seizure outcome as the only factor.Received April 28, 2011. Accepted in final form August 12, 2011.Neurology 78 April 24, 20121297REFERENCES14.Regis J, Kerkerian-Legoff L, Rey M, et al. First biochemi-1.Maruyama K, Kawahara N, Shin M, et al. The risk ofcal evidence of differential functional effects followinghemorrhage after radiosurgery for cerebral arteriovenousgamma knife surgery. Stereotact Funct Neurosurg 1996;malformations. 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Clinical outcome of radiosurgery for cerebralOutcome after interventional or conservative managementarteriovenous malformations. J Neurosurg 1992;77:1- 8.of unruptured brain arteriovenous malformations: a pro-13.Eisenschenk S, Gilmore RL, Friedman WA, Henchey RA.spective, population-based cohort study. Lancet NeurolThe effect of LINAC stereotactic radiosurgery on epilepsy2008;7:223-230.associated with arteriovenous malformations. Stereotact27.The ARUBA Trial. Available at: http://www.arubastudy.Funct Neurosurg 1998;71:51- 61.org/index.html. Accessed April 10, 2011.Neurology(R) Launches Subspecialty Alerts by E-mail!Customize your online journal experience by signing up for e-mail alerts related to your subspecialtyor area of interest. Access this free service by visiting http://www.neurology.org/site/subscriptions/etoc.xhtml or click on the "E-mail Alerts" link on the home page. An extensive list of subspecialties,methods, and study design choices will be available for you to choose from--allowing you priorityalerts to cutting-edge research in your field!1298Neurology 78 April 24, 2012

Radiosurgery for unruptured cerebral arteriovenous malformations

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